A steam turbine is used for the purpose of driving a machine or the like and is provided with a turbine main body that includes a rotatably supported rotor. The rotor is driven to be rotated when steam is supplied to the turbine main body as working fluid. Steam to be supplied to the turbine main body or steam extracted from the turbine main body flows in a steam flow channel of the steam turbine. The steam flow channel is provided with a regulating valve. It is possible to adjust the flow rate of steam to be supplied to the turbine main body by adjusting the openness of the regulating valve.
Furthermore, a steam turbine that is provided with an overload valve in addition to the above-described regulating valve is also known (refer to Patent Document 1 below). In steam turbine equipment described in Patent Document 1, an overload valve is provided on a bypass pipe that branches off from a main steam pipe. It is possible to supply main steam to a middle stage of a high-pressure turbine by opening the overload valve.